United States Nuclear Regulatory Commission - Protecting People and the Environment
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Industry Average Parameter Estimates

NUREG/CR-6928 characterizes industry-average performance for components and initiating events at U.S. commercial nuclear power plants using data available through the end of 2002. Trending studies on this web site indicate that industry performance has generally improved since the 1980s and early 1990s, so the characterization of current industry-average performance is an important step in maintaining up-to-date risk models. Four types of events are covered here: component unreliability (e.g., pump fail to start or fail to run), component or train unavailability resulting from test or maintenance outages, special event probabilities covering operational issues (e.g., pump restarts and injection valve re-openings during unplanned demands), and initiating event frequencies. Typically data for 1998-2015 were used to characterize current industry-average performance, although many initiating events required longer periods (ending in 2015) to adequately characterize frequencies. Results (beta distributions for failure probabilities upon demand and gamma distributions for rates) are used as inputs to the U.S. Nuclear Regulatory Commission's Standardized Plant Analysis Risk (SPAR) models covering U.S. commercial nuclear power plants.

The Detailed Data Sheets provide documentation for each parameter estimate. These data sheets are updates to those originally provided in NUREG/CR-6928.

Note that the System Special Events have not been updated with new data. These estimates are based on system studies that are not regularly updated, and that are largely superseded by the component and system studies that are regularly updated.

2015 Results:

Summary Detailed Data Sheets

2010 Results:

Summary Detailed Data Sheets

Historical Results:

Summary Detailed Data Sheets
Page Last Reviewed/Updated Wednesday, May 31, 2017